1. Field of the Invention
The present invention relates to a spin-injection FET (spin-injection transistor) in which a magnetoresistive effect is utilized.
2. Description of the Related Art
Recently, in addition to magnetic heads and magnetic sensors, a magnetoresistive element in which a magnetic film is utilized is used for advanced-technology devices such as a magnetic random access memory (MRAM), which is of a solid-state magnetic memory and a re-configurable logic circuit.
The spin-injection FET is one mode when the magnetoresistive element is applied to the advanced-technology devices. The spin-injection FET has the feature in that current passed through a channel is changed according to a magnetization state of the magnetoresistive element even if a gate voltage is constant. Further, magnetization reversal caused by spin-polarized electrons is utilized in the spin-injection FET.
For example, the spin-injection FET is used as a memory cell in which data is stored in the magnetic random access memory, and the spin-injection FET is used as an element for realizing one logic gate in the re-configurable logic circuit.
However, in the conventional spin-injection FET, a ferromagnetic body which is of a free layer is in direct contact with a semiconductor substrate and spin-injection current for the magnetization reversal is still as large as about 107 A/cm2, which may result in problems such as generation of thermal disturbance caused by temperature rise in writing and element breakage by the spin-injection current.